initial import of rrd tools - db schema, update and convert functions
add more rrd-related scripts
rrd db: allow more x files
rrd graphs: add kwh and euros to electricy graphs
graph render script
update RRD graph  rendering
Add Flask-based webapp for remote updating of the RRD database.
Create README.md
add 2h graphs
webapp: api keys are useless, stop requiring them; add "last" command for realtime HUD, ...
upd rrd db retention
upd graph rendering script